I think it's a multi-headed monster actually. NO3 defficiency only causes it, once it gets started there's no hope for using NO3 dosing to get rid of it.
The bacteria that causes BGA is free floating until it finds an area where it can start a colony and has enough light and food (it does not need NO3, it can fix nitrogen). This is the phase when NO3 shortages cause it. A lack of NO3 means that there is a lot of other nutrients in the water that the plants can't use, but the BGA can since it can fix nitrogen. As a side note, oxygen will kill this bacteria. This is also why it tends to crop up in dead spots; low oxygen, natural settling place for debris and nutrients. Up until you start to see colonies, it can be prevented through NO3 dosing and keeping water circulation even. This is also where a UV may help to kill the bacteria in the water.
Once it finds a suitable area, it creates a colony enclosed by a membrane. Once it has entered this phase, it begins to grow very rapidly. Cleaning it out will not work since it is bacteria, and you cannot remove bacteria from your tank with any sort of tool. It will just re-establish a colony where it lands again. Dosing NO3 at this point is simply feeding the algae. You will notice huge explosions in growth after fertilizing. Increasing circulation will probably do nothing, since although oxygen is toxic to the bacteria, it is now protected by its membrane. It does work in some situations though, so it's worth a try. The only certain way to get rid of it now is to either do a blackout (which may or may not kill your other plants) or use Maracyn. Maracyn does NOT affect your biological filter if dosed correctly. People think it does because they see a spike in nitrites after treatement. This is due to the mass death of cyanobacteria that just occured in the tank. Just do a water change and your tank should level out in a few days. If the nitrite levels start getting high again, do another water change. If it really damaged the biological filter it would take weeks to recycle.
This is just what I've learned from fighting off BGA and researching it a bit. Really, dosing NO3 and circulation are just preventative measures. They will probably do nothing to combat the algae once it is established.
